feat(promotion code): Promotion code system done

I added the features for users to use promotion code
and for promoters to create on their events.
May be rewrite to discount code?

app/views/promoter/promotion_codes/index.html.erb

@@ -51,7 +51,7 @@
               <div class="flex items-start justify-between mb-4">
                 <div>
                   <h3 class="text-xl font-semibold text-gray-900 mb-2">
-                    <%= link_to promotion_code.code, promoter_event_promotion_code_path(@event, promotion_code), class: "hover:text-purple-600 transition-colors" %>
+                    <%= promotion_code.code %>
                   </h3>
                   <p class="text-gray-600 mb-3">Réduction de <%= number_to_currency(promotion_code.discount_amount_cents / 100.0, unit: "€") %></p>
                 </div>